مدلسازی پاسخ جوانه‌زنی بذر علف‌های‌هرز جودره (Hordeum spontaneum) و علف قناری (Phalaris minor) به دما

نوع مقاله : مقاله پژوهشی

نویسندگان

دانشگاه تهران

چکیده

مدل‌های گوناگونی برای پیش‌بینی پاسخ جوانه‌زنی بذر به دما ارایه شده‌اند که مهمترین و پرکاربردترین آنها مدل زمان گرمایی (یکای گرمایی) است. این مدل اگرچه دارای ویژگی‌های زیست‌شناختی مناسبی برای جوانه‌زنی است ولی بر پایه پیش‌‌فرض‌هایی است که در برخی گونه‌ها (بویژه علف‌های‌هرز) دیده نمی‌شود که برآیند آن پیش‌بینی نادرست جوانه‌زنی است. در این مقاله مدلی بر پایه توزیع آماری ویبول پیشنهاد می‌گردد که نه تنها از نظر زیست‌شناختی بر مدل مرسوم برتری دارد بلکه پیش‌بینی بسیار مناسبی از الگوی جوانه‌زنی نیز فراهم می‌آورد. در پژوهشی آزمایشگاهی جوانه‌زنی بذرهای علف‌های هرز جودره (Hordeum spontaneum) و علف‌قناری (Phalaris minor) در دماهای 8، 12، 16، 20،‌ 24 و 28 درجه سانتی‌گراد آزمون شد و پاسخ جوانه‌زنی آنها توسط هر دو مدل توصیف گردید. مدل مرسوم برازش نامناسبی به داده‌های جوانه‌زنی دو گونه و بویژه علف‌قناری داشت (9 تا 12% خطا). حال آنکه خطای مدل پیشنهادی در این مقاله تنها 4% بود و پیشرفت جوانه‌زنی در طی زمان نیز به خوبی توسط مدل پیش‌بینی شد. مدل پیشنهادی همچنین به خوبی توانست سه پدیده زمان درنگ (زمان تا آغاز جوانه‌زنی)، ‌سرعت جوانه‌زنی و درصد جوانه‌زنی پایانی را در هر دو گونه برآورد نماید. جداسازی تاثیر دما بر سرعت جوانه‌زنی و جوانه‌زنی پایانی از ویژگی‌های مهم این مدل است که به اهمیت بوم‌شناختی آن می‌افزاید. برای نمونه،‌ دمای بهینه برای سرعت جوانه‌زنی در هر دو گونه (در جودره 8/21 و در علف‌قناری 5/23 درجه سانتی گراد) بالاتر از گستره دمایی بهینه بر حسب درصد جوانه‌زنی پایانی بود (در جودره بین 5/7 تا 20 و در علف‌قناری بین 5/7 تا 16 درجه سانتی‌گراد). این ویژگی سازش‌پذیری بسیار بالایی به هر دو گونه برای جوانه‌زنی در دامنه گسترده‌ای از دماهای محیطی می‌دهد.

کلیدواژه‌ها

عنوان مقاله [English]

Modeling the Germination Responses of Wild Barley (Hordeum spontaneum) and Littleseed CannaryGrass (Phalaris minor) to Temperature

نویسندگان [English]

  • Mohsen Beheshtian
  • Hamid Rahimain
  • Hassan Alizadeh
  • sara Ohadi
  • Ahmad Zare
چکیده [English]

Different models have been developed to describe the germination responses of seeds to temperature among which the thermal time (heat unit) model has received the greatest implications. Although biologically relevant, the thermal time model is confined to some assumptions which may not be met in some species (particularly in weed species) and thus can result in poor predictions. In this paper we address a novel Weibull-based model which is not only more biologically relevant but also provides the better predictions of germination compared to the conventional model. Therefore, in a laboratory experiment the seed germination of wild barley (Hordeum spontaneum) and little canary grass (Phalaris minor) was tested at various sub- and super-optimal temperatures including 8, 12, 16, 20, 24 and 28 oC. The both models were then fitted to the data and compared. The conventional thermal time model provided very poor fits to the germination data of both (particularly P. minor) (RMSE = 9% to 12%). However, the new model well fitted to the same datasets with only 4% error (i.e. RMSE). The Weibull-based model was also good at estimating the germination lag, germination rate and final percent germination in either of weeds studied. Separating the effect of temperature on germination rate and germination extent is suggested to be amongst the most significant ecological properties of the model. For example, the optimum temperature for the mid germination rate (21.8 oC in H. spontaneum  and 23.5 oC in P. minor) was found to be higher than and beyond the optimum range of germination extent (7.5 to 20 oC in H. spontaneum  and 7.5 to 16 oC in P. minor). This can give the two species a high degree of germination plasticity in response to the environmental temperatures.  

کلیدواژه‌ها [English]

  • Thermal time model
  • Weibull-based model
  • germination lag
  • Germination rate
  • germination extent

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